I am learning matlab myself andI have made an animated plot using matlab;now i want to save it as an video file.can you tell me how to convert my animation into a video file in matlab.Below is my code
x=[1:2];
for i=1:25,
m=randi([3,5]);
n=randi([3,5]);
y=[m n];
bar(x,y)
axis equal
A(i) = getframe;
end
matlab version 7.8 R2009a
use avifile:
aviobj = avifile('example.avi','compression','None');
x=[1:2];
for i=1:25,
m=randi([3,5]);
n=randi([3,5]);
y=[m n];
bar(x,y)
axis equal
aviobj = addframe(aviobj,gcf);
drawnow
end
viobj = close(aviobj)
If Matlab's avifile doesn't work (it might have problems with codecs of 64-bit OS), then use mmwrite.
http://www.mathworks.com/matlabcentral/fileexchange/15881-mmwrite
It's simple, and it works. I used it to create *.wmv files simply by:
mmwrite(filename, frames);
Edit: code example
% set params
fps = 25;
n_samples = 5 * fps;
filename = 'd:/rand.wmv';
% allocate frames struct
fig = figure;
f = getframe(fig);
mov = struct('frames', repmat(f, n_samples, 1), ...
'times', (1 : n_samples)' / fps, ...
'width', size(f.cdata, 2), ...
'height', size(f.cdata, 1));
% generate frames
for k = 1 : n_samples
imagesc(rand(100), [0, 1]);
drawnow;
mov.frames(k) = getframe(fig);
end
% save (assuming mmwrite.m is in the path)
mmwrite(filename, mov);
One way to do this is to print the figure to an image, and then stitch the resulting image sequence into a video. ffmpeg and mencoder are great tools for doing this. There are some great resources for describing this if you know the right search terms. I like this one
In mencoder, you could stitch your images together with a command like:
mencoder "mf://*.jpg" -mf fps=10 -o test.avi -ovc lavc -lavcopts vcodec=msmpeg4v2:vbitrate=800
Have a look at VideoWriter or see this forum discussion
Related
I am writing a code for a real time experiment using psychtoolbox to present the stimulus. In my experiment, I need to show the subject a graph that indicates his performance. I have plotted the graph using this simple code:
% Draw the graph
figure('visible','off','color',[0 0 0]);
pcolor([0 Num_timepoint+2],[-10 0],ones(2,2));
hold on;
pcolor([0 Num_timepoint+2],[0 10],2*ones(2,2));
colormap([79 167 255;255 187 221]/256);
plot(1:subloop,value0,'*-',...
'color',[0,0,0],...
'LineWidth',1,...
'MarkerSize',5,...
'MarkerEdgeColor','k',...
'MarkerFaceColor',[0.5,0.5,0.5]);
axis([0,Num_timepoint+2,-10,10]);
saveas(gcf,'line_chart.png'); %save it
close(figure);
line_chart=imread('line_chart.png'); %read it
resized_plot=imresize(line_chart,0.5);
imageSize = size(resized_plot);
[imageHeight,imageWidth,colorChannels]=size(resized_plot);
bottomRect = [xCenter-imageWidth/1.5, yCenter+gapdown, xCenter+imageWidth/1.5, yCenter+gapdown+imageHeight];
imageDisplay=Screen('MakeTexture', win0, resized_plot);
Screen('DrawTexture', win0, imageDisplay, [], bottomRect);
Unfortunately, this simple code is very slow. In addition, I couldn't make the graph moving along x axis, as soon as the new value comes.
Any help would be Awesome. Thanks in advance for your efforts.
Why are you saving the figure and redisplaying as an image? Maybe I'm missing something but you should be able to accomplish what you need by updating the existing plot with the fresh data using the handles properties of the plot:
.... First time through we need the initial plot ....
% Set up figure with colormaps and such but leave as 'visible','on'
hPlot = plot(plot(1:subloop,value0,'*-',...
'color',[0,0,0],...
'LineWidth',1,...
'MarkerSize',5,...
'MarkerEdgeColor','k',...
'MarkerFaceColor',[0.5,0.5,0.5]);
hAxes = gca;
.... Loop over your real time updates ....
% Assuming value0 has subject's results from t=0 to t=now
hPlot.XData = value0; hPlot.YData = [1:subloop];
hAxes.XLim = [0 numTimePoints+2];
hAxes.YLim = [-10 10]
.... Continue test and update value0 ....
I think that should keep your plots current without having to save the figure as image to file then reopen the image to display to subject.
If you want to move your data one sample, you can use the circshift function. For example, if you want your new values to appear on the left hand side, you can shift all values 1 sample rightward, then add your new value in the first position.
For converting a MATLAB figure to a Psychtoolbox texture, you don't need to save, then load the temporary images. You can instead use the getframe function to capture the MATLAB figure data, which can then be given to MakeTexture to turn it into a Psychtoolbox texture.
I'm not sure what values you're actually using for subloop, value0, etc. but there is an example that I think might be close to what you want. In this example, 30 frames of figures are plotted, with each figure being on screen for 1 second. New data points are generated randomly and appear from the left hand side of the figure.
Depending on the details of your experiment, you may find that this approach is still too slow. You could also create the figure directly via Psychtoolbox drawing methods like DrawLines, etc. though that would require more effort.
try
win0 = Screen('OpenWindow', 0, 0);
Num_timepoint = 100;
subloop = 100;
value0 = zeros(1,100);
num_demo_frames = 30;
% Draw the graph
fig_h = figure('visible','off','color',[0 0 0]);
pcolor([0 Num_timepoint+2],[-10 0],ones(2,2));
hold on;
pcolor([0 Num_timepoint+2],[0 10],2*ones(2,2));
colormap([79 167 255;255 187 221]/256);
plot_h = plot(1:subloop,value0,'*-',...
'color',[0,0,0],...
'LineWidth',1,...
'MarkerSize',5,...
'MarkerEdgeColor','k',...
'MarkerFaceColor',[0.5,0.5,0.5]);
axis([0,Num_timepoint+2,-10,10]);
for f = 1:num_demo_frames
new_value = randn(1,1);
data_values = plot_h.YData;
data_values = circshift(data_values, 1);
data_values(1) = new_value;
plot_h.YData = data_values;
plot_values = getframe(fig_h);
imageDisplay=Screen('MakeTexture', win0, plot_values.cdata);
Screen('DrawTexture', win0, imageDisplay);
Screen('Flip', win0);
WaitSecs(1);
end
sca;
catch e
sca;
rethrow(e);
end
I try to use matlab 2016a to read avi videos, however, I get the following problems:
undefined funciton or variable 'mmreader';
The code is as following:
clc;
clear;
%% this to read avi by using mmread to get every frame
video = mmreader('D:\My Documents\MATLAB\My\fire.avi');
nFrames = video.NumberOfFrames;
H = video.Height;
W = video.Width;
Rate = video.FrameRate;
% Preallocate movie structure.
mov(1:nFrames) = struct('cdata',zeros(H,W,3,'uint8'),'colormap',[]);
%read one frame every time
for i = 1:nFrames
mov(i).cdata = read(video,i);
P = mov(i).cdata;
disp('current frame number：'),disp(i);
imshow(P),title('original picture');
% P2=rgb2gray(P);
end
Why? Could anyone help me? Thanks in advance.
The function mmreader was deprecated in version R2010b, removed in version R2014a, and removed from the documentation altogether in version R2015b. It was replaced by the VideoReader function, so use that in its place.
I need to save all the captured images in MATLAB but I am able to save one picture at a time.
mycam = webcam();
img = snapshot(mycam);
imwrite(img,'img.jpg');
If somebody knows how to save all the pictures taken at a time in MATLAB, please help me with the code.
I would save the images as a movie and then access the frames later. This is untested but it would work like this.
mycam = webcam();
% if you know the number of images use that here
% a movie is just a collection of frames
% if not then just don't initialize F
F(nFrames) = struct('cdata', [], 'colormap, []);
for i = 1:nFrames
F(i) = im2frame(snapshot(mycam));
end
% save F
movie2avi(F, 'MyMovie.avi', 'compression', 'None');
Then you can load the movie and look at the frames. This example uses the older movie2avi but VideoWriter is also an option
v = VideoWriter('MyMovie.avi');
open(v);
for i = 1:nFrames
writeVideo(v, snapshot(mycam));
end
close(v);
Again untested as I don't have a webcam attached to this computer. But it works for animated graphs. See doc readFrame for the way to read frames
As they have already told you, you should use a for loop with the sprintf function in order to not overwrite the previous images. Try with the following command:
%capture the frames
for i =1:n;% n is the number of frames you want to capture
frames{i} = getsnapshot(mycam);
end
%save in the current folder
for i = 1:n;
imwrite(frames{i}, sprintf('imageName%d.jpg',i))
end
You will have all the captured frames saved in the Current Folder.
I am pretty new to Matlab and encountered a problem when working with images.
I want to get a pixel that is in a specific colour (blue) in the following image:
image
My current code looks something like this:
function p = mark(image)
%// display image I in figure
imshow(image);
%// first detect all blue values higher 60
high_blue = find(image(:,:,3)>60);
%cross elements is needed as an array later on, have to initialize it with 0
cross_elements = 0;
%// in this iteration the marked values are reduced to the ones
%where the statement R+G < B+70 applies
for i = 1:length(high_blue)
%// my image has the size 1024*768, so to access the red/green/blue values
%// i have to call the i-th, i+1024*768-th or i+1024*768*2-th position of the "array"
if ((image(high_blue(i))+image(high_blue(i)+768*1024))<...
image(high_blue(i)+2*768*1024)+70)
%add it to the array
cross_elements(end+1) = high_blue(i);
end
end
%// delete the zero element, it was only needed as a filler
cross_elements = cross_elements(cross_elements~=0);
high_vector = zeros(length(cross_elements),2);
for i = 1:length(cross_elements)
high_vector(i,1) = ceil(cross_elements(i)/768);
high_vector(i,2) = mod(cross_elements(i), 768);
end
black = zeros(768 ,1024);
for i = 1:length(high_vector)
black(high_vector(i,2), high_vector(i,1)) = 1;
end
cc = bwconncomp(black);
a = regionprops(cc, 'Centroid');
p = cat(1, a.Centroid);
%// considering the detection of the crosses:
%// RGB with B>100, R+G < 100 for B<150
%// consider detection in HSV?
%// close the figure
%// find(I(:,:,3)>150)
close;
end
but it is not optimized for Matlab, obviously.
So i was wondering if there was a way to search for pixels with specific values,
where the blue value is larger than 60 (not hard with the find command,
but at the same time the values in the red and green area not too high.
Is there a command I am missing?
Since English isn't my native language, it might even help if you gave me some suitable keywords for googling ;)
Thanks in advance
Based on your question at the end of the code, you could get what you want in a single line:
NewImage = OldImage(:,:,1) < SomeValue & OldImage(:,:,2) < SomeValue & OldImage(:,:,3) > 60;
imshow(NewImage);
for example, where as you see you provide a restriction for each channel using logical operators, that you can customize of course (eg. using | as logical OR). Is this what you are looking for? According to your code you seem to be looking for specific regions in the image like crosses or coins is that the case? Please provide more details if the code I gave you is completely off the track :)
Simple example:
A = imread('peppers.png');
B = A(:,:,3)>60 & A(:,:,2)<150 & A(:,:,1) < 100;
figure;
subplot(1,2,1);
imshow(A);
subplot(1,2,2)
imshow(B);
Giving this:
I am newly working with Matlab. I want to read a video file and do some calculations every frame and display every frame. I wrote the following code but every time it only displays the first frame. can anybody please help.
mov=VideoReader('c:\vid\Akiyo.mp4');
nFrames=mov.NumberOfFrames;
for i=1:nFrames
videoFrame=read(mov,i);
imshow(videoFrame);
end
Note: mmreader API has been discontinued by MATLAB so prefer using VideoReader.
See comment by #Vivek.
I usually do this:
obj=mmreader('c:\vid\Akiyo.mp4');
nFrames=obj.NumberOfFrames;
for k=1:nFrames
img=read(obj,k);
figure(1),imshow(img,[]);
end
As far as your code is concerned, I saw MATLAB's documentation. You should do the things in following order:
mov=VideoReader('c:\vid\Akiyo.mp4');
vidFrames=read(mov);
nFrames=mov.NumberOfFrames;
for i=1:nFrames
imshow(vidFrames(:,:,i),[]); %frames are grayscale
end
Function read() and the field NumberOfFrames() are now deprecated, Matlab suggests using
xyloObj = VideoReader(file);
vidHeight = xyloObj.Height;
vidWidth = xyloObj.Width;
mov = struct('cdata',zeros(vidHeight, vidWidth, 3,'uint8'), 'colormap',[]);
while hasFrame(xyloObj)
mov(k).cdata = readFrame(xyloObj,'native');
end
In case you want to estimate a number of frames in the video, use nFrames = floor(xyloObj.Duration) * floor(xyloObj.FrameRate);
Below suggested code is showing only one frame
imshow(vidFrames(:,:,i),[]);
I am doing following things to store each frame
obj = VideoReader('path/to/video/file');
for img = 1:obj.NumberOfFrames;
filename = strcat('frame',num2str(img),'.jpg');
b = read(obj,img);
imwrite(b,filename);
end
This will store all the frames in your home directory.And yes, as also suggested by Vivek and Parag
You need to use VideoReader as mmreader has been discontinued by
MATLAB.
*=I was making a function to play any .avi file as a set of frames in a figure. Here's what a did. A bit of a combo of what you've done, except my NumberOfFrames wasn't working: (noteL this also shows it in colour)
function play_video(filename)
% play_video Play a video file
% play_video(filename) plays the video file specified by filename in a MATLAB Figure window.
figure
set(figure, 'Visible', 'on')
mov=VideoReader(filename);
vidFrames=read(mov);
duration = mov.Duration;
frame_rate = mov.FrameRate;
total_frames = duration .* frame_rate
for i=1:1:total_frames
imshow(vidFrames(:, :, :, i), []);
drawnow
end